1. Field of the Invention
The invention relates to a high frequency (HF) test prod that includes a housing and a contact unit for electrically contacting at least one contact point of a specimen. An HF coaxial line connects the housing and the contact unit electrically. The HF coaxial line is mechanically arranged between the housing and the contact unit, having an external conductor, an internal conductor arranged coaxially to the external conductor, and a dielectric arranged between the external conductor and internal conductor.
2. Description of Related Art
Generally, with HF test prods, the contact unit, which possesses corresponding contact elements, is used to establish an electrical contact with contact points, such as a planar conductor structure of a specimen, whereby a contact surface and a contact force are necessary in order to establish the electrical contact. In order to allow a predetermined contact force to be applied repeatedly, spring-loaded contact elements are usually provided on the contact unit of the HF test prods. However, in the case of high frequencies these contact elements must, for electrical reasons, be so short that sufficient spring travel is no longer available on the contact elements themselves.
A test prod of this type is known in U.S. Patent Publication No. 2007/0159196 entitled “PROBE FOR COMBINED SIGNALS,” published on Jul. 12, 2007 for Hayden, et al., in which the HF line is designed in the form of a coaxial line. The coaxial line can thereby also provide a spring function for the contacting of the contact unit. However, this has the disadvantage that, due to a temperature-dependent length of the coaxial line, an impedance and an electrical length which influences a phasing of a transmitted HF signal cannot be maintained with the necessary accuracy. The coaxial line also displays a hysteresis when yielding and returning which additionally influences the electrical properties of the contacting in an unforeseeable manner.